Air heater with a plurality of tubes positioned coaxially within one another



June 15, 1965 s ss ETAL 3,189,018

AIR HEATER WITH A PLURALI'IY OF TUBES POSITIONED COAXIALLY WITHIN ONE ANOTHER Filed Oct. 16. 1962 3 Sheets-$heet 1 Fig.1

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HANS 6. $455 HEINRICH HAN/(E WJL, Muiaf mv THE/4Q ATTORNEYS.

I June 15, 1965 H s ss T L 3,189,018

AIR HEATER WITH A PLURAL'ITY 0F TUBES POSITIONED COAXIALLY WITHIN ONE ANOTHER Filed on. 16, 1962 s Sheets-Sheet 2 INVENTORS. fi l/V5 6. $455 HEINRICH HAN/(E 7 IVE/1Q ATTORNEKS.

H. G. SASS ETAL June 15, 1965 AIR HEATER WITH A PLURALITY OF TUBES POSITION COAXIALLY WITHIN our: ANOTHER 3 Sheets-Sheet 3 Filed Oct. 16. 1962 Z It! 1 1 x O a, 3

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United States Patent Office 3,189,618 Fatentecl June 15, 1965 3,18%,018 AIR HEATER WITH A PLURALITY F TUBESPU- SITIUNED CGAXIALLY WITHIN UNE ANUTHER Hans G. Sass, Krefeld, and Heinrich Hanire, Krefelth Uerdinger, Germany, assignors to llndustrie-Companie Kleinewefers Konstruktionsturd Handelsgesellschaft n1.l).H., Krefeld, Germany, a corporation of Germany Filed Oct. 16, 1962, Ser. No. 230,931 Claims priority, application Germany, Nov. 26, 1951,

.1 26,858 v 11 Claims. (Cl. 126-116) This invention relates to air heaters which have a pinrality of shells or cylinders positioned coaxially within 1 one another. In heaters of this type, which also are known as gap air heaters, the air to be heated travels through an air passageway and the heating gases, resul ing from combustion of a fuel, flow through a gas passageway with the direction of flow of air to gas being con- 1 current and/or countercurrent. These air and gas passageways are formed by the shells arranged coaxially Within one another and in their flow through the heater, the air and gas are not intermingled but are kept separate from one another to effect a heat exchange between the hot gases and the air to be warmed. In some heaters, the cylinders or shells are several meters long or high whereas the gap width or the interstitial space between the cylinders is selected from a range of about a few centimeters up to about centimeters.

One problem encountered in construction, assembly and operation of these heaters has been maintenance of a sub stantially uniform gap width between successive coaxial shells to provide a desired sustained volume and velocity of flow of air and gas in the passageways. A narrowing of this gap decreases the velocity of flow and heat exchange between the gases and the air in directly affected upon a change in the flow velocity. Thus, variation in flow velocity in the passageways between the shells effects uneven heating in the tubes which, in turn, generates stresses in the shells themselves. Consequently, during a prolonged period of operation, leaks may occur in the cylinders which are stressed, thereby preventing the separation between the heating gases and the air. Furthermore, seams in the shell walls need to be protected from stresses in the tubes to assure gas and air tightness in the air and heating gas passageways.

Since the shells are positioned within one another, maintenance of this uniform gap width is further complicated by the different heating rates to which the shells are subjected. The gap width between the cylinders should remain, if at all possible, substantially the same for each medium so that differential heating of the coaxial shells can be taken into consideration when positioning same in the heater. 'As the number of shells positioned within one another increases, difficulties in manufacture and assem bly of the heater increases. Also, if it is desirable to have a long passageway for the air and heating gas, a large number of shells must be disposed within one another. Accordingly, the cylinders or shells must have a mounting which permits expansion and contraction due to their'subjection to different temperatures of gas and air. 7

It has been found that only with great difficulty is it possible to suspend a large number of cylinders from a shell or casing of a heater and simultaneously maintain the desired gap width between the cylinders. This is par-' ticularly true because a cylinder may be subjected to the hot pro-ducts of combustion of the fuel on one side and to the air to be warmed on the other'side so that a single individual cylinder can encounter two different mediums, each at a different temperature to effect changes dimensionallyboth longitudinally and radially due to expansion and contraction.

t isthe aim of this invention to improve air heaters having a plurality of shells inserted within one another for the purpose of guiding the air to be heated and the heatiug gas. To attain this aim in an air heater of the abovementioned type in accordance with the invention, one portion of the guide shells is connected to a heater bell which together with its shells is removabale from the casing of the heater and the other guide shells are connected to the heater casing. Preferably in this case the bell is provided with an additional annular channel removably connected to the upper conventional annular channel of the casing.

The bell of the invention is also provided with a central air collection chamber surrounded by a supplementary annular chamber.

In order in simple fashion to center the shells which can be removed from the casing in conjunction with the bell, centering means are provided between the inner tubes connected to the heater shell and the outer tubes connected to the heater bell. These centering means consist of curved portions or the like provided on the outer surface of the one tube and of a fillet, rod, or the like secured to the inner surface of the other tube with the fillet or rod having a fixed or an adjustable pitch.

In the accompanying drawings we have shown a preferred embodiment of our invention in which:

FIGURE 1 is a vertical section view of an air heater which has our invention;

FIGURE 2 is a sect-ion view along the line II-II of FIGURE I;

FIGURE 3 is a partial section View in the same plane as that of FIGURE 2 showing one centering means for the tubes connected to the bell ofthe heater of FIG- URE 1;

FIGURE 4 is a section view along the line IVIV of FIGURE 3 and FIGURE 5 is a view similar to FIGURE 1 showing the bell and its tubes detached and partially removed from the shell of the heater.

Referring to FIGURES 1-5, the outer part of the heater is formed by an outer insulated casing 1, surrounded by from four'to six supporting rods 2 resting at their lower ends on a foundation (not shown) and carrying a flange 13 of the casing l on their upper ends. The lower end of the heater, whose bottom is designated by reference numeral 3, is provided with a flame entry port 4 and an explosion recess 5 having a hinged'cover. in the lower portion of the heater is located a lower annular chamber or first air collection chamber 6 into which the air to be heated is conducted by means of a connecting piece '7 in the direction of arrow 8. Similarly, the upper portion of the heater is equipped with an annular chamber 9 provided with a connecting piece 1t) which is bent upwardly at 11 and has a flange 12.

Secured to the flange 13 is an annular shell 15 coaxially positioned in relation to an outer annular shell 14. The

lower end of shell 15 is sealingly connected by a compensating ring 16 to the bottom or end wall 6a of the lower annular chamber 6. This ring 16 is in the form of an outwardly flaring flange which permits both radial and longitudinal expansion of the shell 15. In its center, shell 14 is secured to casing 1 by a compensating necked portion 17. Thus both cylinders or shells 14 and 15 are joined to casing 1 or its closing flange 13 in such a mannor that they are able to expand sufficiently under thermal change, in a longitudinal direction. a

The bell of the heater, generally designated by reference numeral 20 is provided on its upper side with an exhaust pipe 21 secured by means of a flange, and on its annular underside with a flangeZZ. This flange 22 is supported on the flange 13 of the casing 1 by the interposition of suitable conventional sealing means and may be connected to the casing. The bell 20 has a conical shell portion 29 carrying a coaxially positioned cone 23 whose lower end is in alignment with an upper end of the shell when the bell is positioned as shown in FIGURE 1. Spacing means (not shown) separate the cone 23 by a first narrow space or cone gap from a second cone 24 to whose lower end 24a (see FIGURE 5) an outer annular wall 25 is connected. The cone 24 and the wall 25 are securely interconnected with one another and with the bell. The cone 24 surrounds a supplemental annular chamber 26 into which an air collection chamber 27 projects coaxially and into which a supply line 23 empties. This supply line 28 is bent downwardly and has its flange 28a removably joined to the flange 12. The annular chamber 26 is inwardly limited by a flat cone 30 to whose rim an intermediate annular wall 31 is joined. The cone 30 and the Wall 31 are also connected to the bell by means of spacers or similar installations.

A second annular cone gap is formed between the cone 30 and a second flat cone 32 with the gap being connected upwardly to the air collection chamber 27, and connecting downwardly into an inner annular gap formed by the wall 31 and an inner annular wall 33 which is, in turn, connected to the bell. As shown in FIGURE 1, the lower end of the second flat cone 32 is joined to the upper end of the wall 31 and this cone 32 and the wall 33 form a generally cylindrical combustion chamber 36. The lower ends of the walls and 33 are of such configuration that, as will be explained hereinafter, the air to be heated is able to pass from one annular gap to the other. For this purpose the lower ends of Walls 25 and 33 are interconnected by end wall 34 with one another, and wall 31 is of shorter length at this point than the other two abovementioned walls. Thus, the walls 25, 31 and33 have ability to expand in a downward direction and are suspended by the bell 20.

As shown in the drawings, the shells 14, 15 and walls 25, 31 and 33 are positioned coaxially within one another.

The air to be warmed travels as follows: by way of supply pipe connector 7 the air to be heated flows into the annular chamber 6 and at the lower ends of shells 14 and 15 arrives in the annular gap between said shells, from where it flows upwardly into the annular chamber 9, through connector 10 and supply line 28 into the supplemental annular chamber 26. From here the air is conducted into an outer annular gap formed between walls 25 and 31, at whose lower end the direction of flow is reversibly deflected and the air enters the inner annular gap located between walls 31 and 33. In the course of its upward flow through the inner gap, the already heated air is acted upon directly by the flame or the heating gases which are on the opposite side of the wall 33. By way of the second annular cone gap formed between cones and 32, the air reaches chamber 27 and flows from there into an exit pipe 35. Thus, the air to be warmed traverses an air passageway formed by shells 14 and 15, chamber 9, connector 10, supply line 28, chamber 26, walls 25 and 31 and walls 31 and 33 to the chamber 27.

The products of combustion which constitute the heating gas flow as follows: the gases from the upwardly directed flame 37 in the combustion chamber 36 first are deflected by the closed top of the cone 32 in a downward path which surrounds the flame as indicated by arrows 38, and then the gases flow radially outwardly into the space between the shell 15 and wall 25. Next, the gases travel between shell 15 and wall 25 into the first annular cone gap between the cones 23 and 24, and from there to the exhaust line 21. As may be seen particularly from FIGURE 1, walls 25 and 33 are of shorter length than shell 15.

When flanges 13 and 22, as well as flanges 12 and 28a are unfastened, bell 20 may be removed vertically from the air heater, and walls 25, 31 and 33 are lifted out of shells 14 and 15. Of course, the bell-connected tubes may also be installed by fastening the flanges 13 and 22 and 12 and 28a together. Whereas on the one hand shells 14 and 15 may be positioned from one another and on the other hand walls 25, 31 and 33 may be positioned from one another by means of suitably installed spacers, means for centering a group of shells 14 and 15 and a group of walls 25, 31 and 33, in relation to one another are provided as shown in FIGURES 3 and 4. These centering means comprise curved lug members 40, approximately a hands breadth long, arranged at intervals from one another in the vicinity of the lower end of Wall 25. These curved members which may be made of steel rounds in wellknown manner are located in the same horizontal plane. At the same elevation as these curved portions, a like number of narrow plates or strips 41 is provided. When these strips 41 are securely fastened to the shell 15, selection of their angle of inclination a in relation to the wall of shell 15 takes into account the ditference between the longitudinal expansion and the radial expansion of the shell 15 and of the wall 25. In making this selection, one considers that the individual shells are exposed on one side to smoke and hot gases and on the other side to the air to be warmed and that both the longitudinal expansion and the radial expansion of the wall 25 are greater than that of the shell 15. Thus, the lug members 40, which are all at the same elevation, are moved not only radially outwardly, but also downwardly by the expansion of the wall 25. Accordingly, the strips 41 are so located that when the heater is cool or at ambient temperature, the lug members 40 are positioned above the strips 41, and when the heater is in operation, these lug members 41 and the strips 41 are opposite one another as shown in FIGURE 4. Additionally, there is the fact that the hot gases are substantially warmer at 34 than at the exhaust 21 and the air is materially cooler at the intake 7 than at the exit pipe 35. As a consequence, the individual tubes experience different amounts of longitudinal and radial expansion.

When the strip 41 is swingably constructed, then one or more positioning rods 42 penetrates through the shell 1 in order to permit ready centering of the walls 25, 31 and 33 from outside the heater. The schematically shown adjustability of strip 41 may preferably be executed in such a way that the strip is secured in its guide aperture 43, and an externally protruding end of rod 42 may be dispensed with. Then guide aperture 43 may be sealed in a heat insulating manner.

Our invention has important advantages which include a bell which is rernovably joined to the shell of the heater and which mounts a first group of the plurality of coaxial tubes disposed within one another. Thus, our heater can maintain a desired gap width for the bell forms a good support for the first group tubes and suspends them so that they can expand downwardly in response to changes in the temperature of the medium or mediums contacting same. In this way, generation of stresses in the tubes from inability to expand is avoided. Additionally, the bell with its first group of shells attached thereto provides easy and eflicient cleaning of the heater for soot and cinder from the fuel have a tendency to settle on the cylinder walls and must be removed for efiicient heat exchange between the hot gases and the air.

The centering means for positioning the first group of tubes relative to the second group of shells which are attached to the shell enables one to take into account differences in radial expansion between the shells of the first group and those of the second group and thereby maintain the gaps between the shells at a given width.

While we have shown and described a preferred embodiment of our invention, it may be otherwise embodied within the scope of the following claims.

We claim:

1. In an air heater having an outer casing and a generally cylindrical combustion chamber for burning fuel therein, the improvement comprising an air inlet and an air outlet of said casing, a plurality of spaced apart shells disposed substantially coaxially of said combustion chamber and of each other, the innermost of said shells being closed at its upper end by an end wall and forming said combustion chamber, the outermost of said shells defining on one side thereof with the interior wall of said casing a first portion of an air passageway for flow therethrough of air to be warmed and defining on the other side thereof with the next most outer shell a portion of a gas passageway for (flow of products or" combustion theretbrough, end means closing the space between both ends of said outermost shell and said casing, said air inlet having an opening into said first portion of said air passageway, said next most outer shell and said innermost shell terminating short of the bottom of said heater and having an end wall member joined to the lower ends thereof and closing the space therebetween to form a second portion of said air passageway, duct means connecting said first and second portions of said air passageway for flow of air therethrough, said gas passageway having a connection with said combustion chamber and exhaust, said casing having an upper portion and a lower portion, means for removably supporting said upper portion of said casing upon said lower portion whereby said upper portion is liftable substantially vertically from said lower portion, a first part of said shells being mounted in suspension by and depending from said upper portion of said casing and a second part of said shells being mounted by said lower portion of said casing, said lower portion of said casing including a flame entry port extending therethrough into said combustion chamber. 1

2. The improvement of claim 1 characterized by an intermediate shell disposed between said innermost and said next outermost shells and spaced apart therefrom, one end of said intermediate shell terminating short of said end wall which joins said innermost and said next outermost shells and an end wall closing the space between said intermediate and said next outermost shell substantially adjacent the other end of said intermediate shell to form a concurrent part and a countercurrent part of said air passageway, said air outlet being connected into that part of said air passageway formed by said intermediate and innermost shells and said duct means being connected into that part of said air passageway formed by said intermediate and next outermost shells.

3. The improvement of claim 2. characterized by said inner, intermediate and next outermost shells being mounted by said upper portion of said casing.

4. The improvement of claim 3 characterized by air collection chamber means and air distribution chamber means located in said upper portion of said casing and arranged coaxially within one another and in connection with said air passageway, said air outlet being connected into one of said chamber means, positioning means interposed between said outermost shell and said next outermost shell to locate said next outermost shell radially relative to said outermost shell, said positioning means comprising lug members afiixed to the exterior surface of said next outermost shell in spaced apart locations and strip members connected to said outermost shell, in engagement with said lug members when said heater is in operation and said next outermost shell has expanded more than said outermost shell and mounted for adjustable movement toward and away from said next outermost shell, said lug members being disposed above and out of engagement with said strip members when said heater is at ambient temperatures and being further disposed in engagement with said strip members as said next outermost shell expands during heater operation.

5. The improvement of claim 2 characterized by positioning means interposed between said outermost shell and said next outermost shell to locate said next outermost shell radially relative to said outermost shell, said positioning means comprising lug members aflixed to the exterior surface of said next outermost shell in spaced apart locations and strip members connected to said outermost shell, in engagement with said lug members When said heater is in operation and said next outermost shell has expanded more than said outermost shell and mounted for adjustable movement toward and away from said next outermost shell, said lug members being disposed above and out of engagement with said strip members when said heater is at ambient temperatures and being further disposed in engagement with said strip members as said next outermost shell expands during heater operation.

6. The improvement of claim 5 characterized by positioning means interposed between said outermost shell and said next outermost shell to locate said next outermost shell radially relative to said outermost shell, said positioning means comprising lug members affixed to the exterior surface of said next outermost shell in spaced apart locations and strip members connected to said outermost shell, in engagement with said lug members when said heater is in operation and said next outermost shell has expanded more than said outermost shell and mounted for adjustable movement toward and away from said next outermost shell, said lug members being disposed above and out of engagement with said strip members when said heater is at ambient temperatures and being further disposed in engagement with said strip members as said next outermost shell expands during heater operation.

'7. The improvement of claim 1 characterized by air collection chamber means and air distribution chamber means located in said upper portion of said casing and arranged coaxially within one another and in connection with said air passageway, said air outlet being connected into one of said chamber means.

8. The improvement of claim 7 characterized by a second air collection chamber disposed in the lower portion of said casing and interconnected with said air inlet and said first portion of said air passageway.

9. The invention of claim 1 characterized by positioning means interposed between said outermost shell and said next outermost shell to locate said next outermost shell radially relative to said outermost shell.

10. The improvement of claim 9 characterized by said positioning means comprising lug members afiixed no the exterior surface of said next outermost shell in spaced apart locations and strip members connected to said outermost shell, in engagement with said lug members when said heater is in operation and said next outermost shell has expanded more than said outermost shell and mounted for adjustable movement toward and away from said next outermost shell, said lug members being disposed above and out of engagement With said strip members when said heater is at ambient temperatures and being further disposed in engagement with said strip members -as said next outermost shell expands during heater operation.

11. The improvement of claim 1 characterized by said upper portion of said casing being a bell.

References Cited by the Examiner UNITED STATES PATENTS JAMES W. WESTHAVER, Primary Examiner.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,189,018 June 15, 1965 Hans G. Sass et a1.

It is hereby certified that error appears in the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

column 1, line 35, for "in" read is lines 38 and 44, for "tubes", each occurrence, read shells column 3, line 1, for "shell" read casing column 4, line 62, for "tubes" read shells Signed and sealed this 23rd day of November 1965.

QSEAL) Atlest:

ERNEST W. SWIDER EDWARD J BRENNER Attesting Officer Commissioner of Patents 

1. IN AN AIR HEATER HAVING AN OUTER CASING AND A GENERALLY CYLINDRICAL COMBUSTION CHAMBER FOR BURNING FUEL THEREIN, THE IMPROVEMENT COMPRISING AN AIR INLET AND AN AIR OUTLET OF SAID CASING, A PLURALITY OF SPACED APART SHELLS DISPOSED SUBSTANTIALLY COAXIALLY OF SAID COMBUSTION CHAMBER AND OF EACH OTHER, THE INNERMOST OF SAID SHELLS BEING CLOSED AT ITS UPPER END BY AN END WALL AND FORMING SAID COMBUSTION CHAMBER, THE OUTERMOST OF SAID SHELLS DEFINING ON ONE SIDE THEREOF WITH THE INTERIOR WALL OF SAID CASING A FIRST PORTION OF AN AIR PASSAGEWAY FOR FLOW THERETHROUGH OF AIR TO BE WARMED AND DEFINING ON THE OTHER SIDE THEREOF WITH THE NEXT MOST OUTER SHELL A PORTION OF A GAS PASSAGEWAY FOR FLOW OF PRODUCTS OF COMBUSTION THERETHROUGH, END MEANS CLOSING THE SPACE BETWEEN BOTH ENDS OF SAID OUTERMOST SHELL AND SAID CASING, SAID AIR INLET HAVING AN OPENING INTO SAID FIRST PORTION OF SAID AIR PASSAGEWAY, SAID NEXT MOST OUTER SHELL AND SAID INNERMOST SHELL TERMINATING SHORT OF THE BOTTOM OF SAID HEATER AND HAVING AN END WALL MEMBER JOINED TO THE LOWER ENDS THEREOF AND CLOSING THE SPACE THEREBETWEEN TO FORM A SECOND PORTION OF SAID AIR PASSAGEWAY, DUCT MEANS CONNECTING SAID FIRST AND SECOND PORTIONS OF SAID AIR PASSAGEWAY FOR FLOW OF AIR THERETHROUGH, SAID GAS PASSAGEWAY HAVING A CONNECTION WITH SAID COMBUSTION CHAMBER AND EXHAUST, SAID CASING HAVING AN UPPER PORTION AND A LOWER PORTION, MEANS FOR REMOVABLY SUPPORTING SAID UPPER PORTION OF SAID CASING UPON AID LOWER PORTION WHEREBY SAID UPPER PORTION IS LIFTABLE SUBSTANTIALLY VERTICALLY FROM SAID LOWER PORTION, A FIRST PART OF SAID SHELLS BEING MOUNTED IN SUSPENSION BY AND DEPENDING FROM SAID UPPER PORTION OF SAID CASING AND A SECOND PART OF SAID SHELLS BEING MOUNTED BY SAID LOWER PORTION OF SAID CASING, SAID LOWER PORTION OF SAID CASING INCLUDING A FLAME ENTRY PORT EXTENDING THERETHROUGH INTO SAID COMBUSTION CHAMBER. 